Universal mandrel



Dec. 8, 1959 F. J. FucHs, JR

UNIVERSAL MANDREL Filed Jan. 24, 1956 INVENTOR Francis J. Fuchs) J'l.;-

BY @.Q.

ATTORNEY United States Patent Office 2,916,077 Patented Dec. 8, 1959 UNIVERSAL MANDREL Francis J. Fuchs, Jr., Winston-Salem, N.C., assignor to Western Electric Company, Incorporated, New York, N .Y., a ,corporation of New York Application January 24, 1956, Serial No. 561,057

4 Claims. (Cl. 153-63) This invention pertains to a mandrel for bending hollow tubular bodies and more particularly to a liexible mandrel used in bending Wave guide tubing.

High frequency electromagnetic energy is commonly transmitted by means of thin-walled rectangular tubes or wave guides. Such wave guides will transmit two general types of electromagnetic waves, namely so-called E waves and H waves, the former having an electrical field component in a plane parallel to the narrow side of a transmitting wave guide and the latter having a magnetic field component in a plane parallel to the broad side of the wave guide. Consequently, the wave guide which is bent with the narrow sides thereof remaining in the same plane is termed an E bend and a wave guide Which is` bent with the broad sides thereof remaining in the same plane is termed an H bend. In bending hollow tubes for wave guides, large tensile and compressive stresses are developed within the walls of the tube which may cause buckling or collapse at the place offbend. In order to overcome buckling and other difficulties and to preserve as far as possible the original interior cross-sectional dimensions of the tube, it lis necessary while effecting such bends in the wave guides to uniformly support the interior thereof with a flexible mandrel. The end of the supporting mandrel must therefore be flexible so that it may bend with the tube and be easily extracted after the bending operation is completed.

Therefore, it is an object ofthe present invention to provide an articulated mandrel for supporting the interior of a rectangular wave guide tube during the bending thereof.

It is another object of the present invention to provide a mandrel for supporting the interior of the wave guide tube while the tube is bent into the form ofeither an E or H bend of relatively small radius, for example, approximately inch or 3,41 inch, respectively.

It is a further object to provide a tube bending mandrel having great mechanical strength and capable of providing uniform interior cross-sectional dimensions of the wave guide being bent.

In accordance with the above objects, the preferred embodiment of the present invention comprises a rigid stern and a iiexible body portion secured to one extremity thereof. The iiexible body portion comprises a plurality of links being alternately pivotally and slidably secured to each other to permit bending the mandrel in the direction of either an E or an H bend.

Other objects and features of the present invention will be more readily understood'from the following detailed description when taken in conjunction with the accompanying drawings, in which:

j Fig.l 1 is a top'plan view, partly in section, of the actuated mandrel in the form of an H bend;

Fig. 2 is an enlarged cross-sectional View of the'actuated mandrel taken on the arcuate line 2--2 of Fig. l;

Fig. 3 is an enlarged exploded top plan View, partly in section, of the several links of the flexible body portion ,of the mandrel;

Fig. 4 is an enlarged cross-sectional view of the several links of the exible body portion of the mandrel taken on line 4--4 of Fig. 3;

Fig. 5 is an enlarged fragmental view of an extremity of the rigid stem to which the flexible body portion of the mandrel is secured, and

Fig. 6 is an enlarged View of the extremity of one portion of the rigid stem looking in the direction of line 6-6 of Fig. 5.

Referring now to the drawings wherein similar reference numerals designate corresponding parts throughout the several views and particularly to Figs. 1 and 2 thereof, in which the mandrel, preferably constructed of Nitralloy steel, comprises a first or terminating link, designated generally -by the numeral 11, having a rounded forming end 12 thereon, portions of which support the interior surface of the tubular member during theV bending operation and during the extraction of said mandrel subsequent to the bending of an E bend, and rounded side surfaces 13, portions of which support the narrow sides of the tubular member during and subsequent to the bending of an H bend. The terminating link 11 also is provided with an arcuate T-shaped slot 14 to accommodate T-shaped projections 16-16 on a second link, designated generally by the numeral 17, to slidably secure the first link 11 to the second link 17 and thus permit actuation of said links with respect to each other during the formation of an H bend in the tubular member. The first link 11 has a cut out section 18 on one or both sides of said link to permit the first link 11 to slide with respect to the second link 17, which movement will be limited by a cylindrical portion 19 of the second link 17 abutting the material forming the end of the T-shaped slot 14 in the rst link 11. lt should be noted that if it is desirable to actuate the first link 11 with respect to the second link 17 in either direction, it will be necessary to have a cut out portion 18 on the opposing side as shown in the drawing (see Fig. 3); but if the mandrel is to be bent only to the left as shown in Fig. l, only one cut out portion 18 need be provided on the left-hand portion of the first link 11. It should also be noted that the amount to be cut outl in portion 18 will be determined by the minimum radius of bend desired and thus forms a limiting stop for the actuation of the first link 11 with respect to the second link 17.

The second link 17 comprises two juxtaposed sections 22 and 23 (Fig. 3) secured together by screw means 24 to permit separation of said sections 22 and 23 to facilitate the insertion of the T-shaped projections 16-16 of said second link in the T-shaped slot 14 in the first link 11, and to facilitate the insertion of inwardly extending cylindrical projections 26-26 upon the substantially cylindrical supporting portions 19-19 in a slot 27 of a third link, designated generally by the numeral 28, to slidably secure the irst link `11 to the second link 17 and pivotally secure the second link 17 to the third link 28. The second link 17 ,has rounded surfaces 29-29 on opposing ends of the substantiallycylindrical supporting portions 19-19 to support the inside surface of a tubular member being bent in an H bend. The side surfaces 3ft-30 of the cylindrical supporting portions 19-19 are to support the inside surface of the tubular member when such member is being formed into an E bend. The secondlink 17 has a cut out portion 31 which slidably accommodates a T-shaped projection 32 of a fourth link, designated generallyV by the numeral 33, to permit the insertion of the .fourth link 33 into the third link 28. It should be noted that the last mentioned cut out portion 31 may be eliminated, since the fourth link 33 could be inserted and removed from the third link 28 merely by separating the two halves of the second link 17 and removing the second link 17 from the third link 28 during assembly and disassembly. The cut out portion 31 merely eliminates the necessity of the above operation.

The third link 28 is a unitary member having the slot 27 to accommodate 'the insertion of the cylindrical projections 26-,26 to pivotally secure the second link 17 to the third link 28 and to form part of an arcuate T- shaped slot 34 to slidably accommodate the arcuate T-shaped projection 32 on the fourth link 33. A portion of the slot 27 is preferably obstructed by a portion 36 of the material forming the link to provide a stronger link, thus preventing separation of portions 37 and 38 of the link 28 forming the opposing sides of the slot 27 when the mandrel is being used to form and E bend. The amount of material remaining in the slot will also determine the desirable length of the cylindrical projections 26-26 in the second link 17.

The fourth link 33 comprises a cylindrical body portion 39 and the arcuate T-shaped portion 32 projecting therefrom. The T-shaped projection 32 is slidably secured in the T-shaped groove 34 of the third link 28 and is also slidable in the cut out portion 31 of the second link 17. The end of the T-shaped projection 32 is provided with an arcuate groove 41 having an semicircular cross section to slidably accommodate portions of cylindrical projections 26-26 of the second link 17 during the bending operation. The T-shaped projection 32 on the fourth link 33 may have both sides thereof terminating in the same plane as the ends of the cylindrical body portion 39 which would necessitate providing a cut out portion similar to the cut out portion 31 in the opposing side of the second link 17 to permit movement of the second link with respect to the fourth link 33. However, it is preferable to terminate one side of the T-shaped projection 32 in the same plane as one end of the cylindrical body portion 39 and terminate the other side 43 of the T-shaped projection 32 in a plane oriented at an acute angle with respect to the plane formed by the opposing end of the cylindrical body portion 39, thus allowing the mandrel to be bent to the left and necessitating only the one cut out portion 31 in the second link. The cylindrical body portion of the fourth link 33 has cut away portions 44 and 46 on opposing sides thereof to permit the third link 28 to be slid on the T-shapedprojection 32 of the fourth link 33 and is provided with a central bore 47 to accommodate the insertion of cylindrical projections 48 and 49 adjacent the end of a rigid stem, designated generally by the numeral 51, to pivotally secure the fourth link 33 to the rigid stem 51 and permit movement of the fourth link 33 with respect to the rigid stern S1 during the forming of an E bend.

The rigid stem 51 comprises two juxtaposed portions 52 and 53 which are held together by screw means 54 and dowel means 56 in a threaded bore 57 and an Unthreaded bore 58, respectively. The portions of the rigid stem have the two cylindrical projections 48 and 49 adjacent the end thereof contact each other at the longitudinal centerline of said stem SI1 to form an arcuate passage 59 and a shaft, designated generally by the numeral 61, to accommodate pivotal mounting of the flexible body portion to the rigid stern 51. An aperture 62 is formed in the opposing end of the rigid stem 51 to accommodate a reciprocating mandrel shaft 75 to assist in the insertion and removal of the mandrel from the tubular member subsequent to the .bending operation.

The bifurcated portion 53 of the rigid stem 51 is terminated ina plane forming an obtuse angle with respect to the side 63 of the rigid stem 51 to allow clearance for the cylindrical forming portion 19 of the second link 17 when moved with respect -to the rigid stem 51 and to allow the third link 28 to be moved with respect to the rigid stem 51, whereby such movement islimited to control the minimum radius of curvature of the H bend by the abutmentof the surfaces 64 and 66 on the near end of the third link 28 abutting a portion 67 of the terminating end of the rigid stem. The second bifurcated portion 52 of the rigid stem 51 is terminated in a plane perpendicular to the sides of the rigid stem and has a curved surface 68 to form a support for an interior portion of the tubular member during the formation of an H bend. Both ends of the bifurcated portions 52 and 53 forming the broad sides of the rigid stern 51 have curved surfaces 69 and 71 (Fig. 6) to support the interior surface of the tubular member during the formation of an E bend.

The first link r11 and third link 28 are provided with convex and concave arcuate surfaces 72-73 and 74-76, respectively, meeting on a line tangent to said arcuate surfaces to support the broad interior sides of the tubular member during the formation of an E bend.

In the operation the rigid stem 51 of the assembled mandrel is connected in the aperture 62 (Fig. l) at the extremity thereof to a reciprocating mandrel shaft 75 and the mandrel is fed forwardly into the `interior of a tubular member (not shown) to be bent by appropriate apparatus (not shown) which is well known in the art.

The bending apparatus (not shown) is actuated to bend the ltubular member into a small radius bend either of an H or `an E bend; if an H bend is formed the links comprising the flexible body portion pivot and .slide in the connections therein to assume the configuration of the bent tubular member, thereby affording support to the interior thereof, and if an E bend is formed the links comprising the flexible body only pivot on .the appropriate connections to assume configuration of :the bent tubular member thereby affording support to the interior thereof. At the completion of the bending operation the mandrel is retracted from the bent tubular member and the tubular member is then removed from the bending apparatus.

Although only four links are disclosed in the drawings of the mandrel it is apparent that more could be provided which would necessitate placing links similar to the second and third links 17 and 28, respectively, between the third and four-th links 28 and 33, respectively, except the T-shaped portion on a similar second link would need -to have an arcuate groove similar to the groove 41 in the fourth link 33 to allow the cylindrical projections 26-26 to slide with respect to `the added link similar to the second link 17. It is obvious that the tube bending mandrel could be formed entirely of flexible links or in a reverse sequence whereby an end of the rigid stern would be formed similar yto the slotted end of the terminating link 11, thereby slidably `securing the exible body portion to the rigid stem instead of pivotally securing the same.

The links of the mandrel are interconnected as disclosed to form a mandrel which will withstand extreme forces without breakage. The cylindrical portions 26-26 48 and 49 could be replaced by separate pins or with a projection on one part to fit in an aperture on the other, but it has been found advantageous to form such pivotal members in the portions of the link 17 or stem 51 from the same piece of material. It should be .noted that if a single pin were used on the rigid stem instead of the two cylindrical projections 48 and 49, as shown, the rigid stem 51 could well be one portion instead of the two portions 52 and 53, as shown.

I-t is to be understood that the above described arrangements are simply illustrative of the application of the principles of `the invention. Numerous other arrangements may be readily devised by those skilled in the art which would embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

l. A tube bending mandrel comprising a rigid stem and a flexible body, said stem having two juxtaposed portions and a shaft extending between said juxtaposed portions to receive `and to pivotally secure one extremity of `the flexible body thereto, said flexible body comprising a plurality of links, a rst link of said body portion being pivotally `secured to said rigid stem comprising a unitary member having a centrally bored cylindrical body portion and an arcuate T-shaped projection having an arcuate slot of a semicircular cross section in the end thereof extending perpendicular to the longitudinal centerline of said bored body portion, a second link of said body having a slot therein and a rounded forming end portion and a concave arcuate side surface tangential to said rounded end slidably secured to the T-shaped projection of said first link by an arcuate T-shaped slot in said second link for relative movement between said rst and second links in a first plane, a third link of said body comprising two juxtaposed portions meeting on the longitudinal centerline of said mandrel having a plurality of cylindrical projections extending inwardly towards said centerline to pivotally secure said third link in the slot in said second link for relative movement between said second and third links in a second plane, an arcuate T- shaped projection on said third link to slidably secure said third link to a fourth link of said body for relative movement between said third and fourth links in said frst plane, said rst plane being perpendicular to said second plane, said fourth link having at least one cut out portion to permit movement of said fourth link with respect to said third link, a rounded convex forming end on said fourth link, a concave arcuate forming side surface meeting said rounded end at the line of tangency of said rounded end, means to secure the two portions of said third link together, and means to secure the two juxtaposed pontions of the rigid stem together, thereby pivotally securing said exible body to said rigid stem and alternately pivotally and slidably securing the links of said exible body one to the other to forma exible tube bending mandrel which will bend in mutually perpendicular planes.

2. A tube bending mandrel comprising a rigid stem, a exible body portion comprising a plurality of links secured adjacent the end of said rigid stem, means to secure said exible body portion to said rigid stem, a first link of said body portion comprising a cylindrical body portion and a T-shaped projection extending from the side thereof, a second link of said body portion secured to said first link by the reception of said T-shaped projection in an arcuate T-shaped slot in said second link for relative movement between said first and second links in a rst plane, a third link of said body portion being pivotally secured to said second link for relative movement between said second and third links in a second plane and slidably secured to a fourth link of said body portion for relative movement between said third and fourth links in said rst plane, said first and second planes being mutually perpendicular, said third links comprising a plurality of juxtaposed portions secured to each other by securing means, and said fourth link having an arcuate T-shaped slot adjacent the end thereof, whereby the links of said exible body portion are alternately slidably and pivotally secured to each other and to said rigid stem to form a ilexible tube bending mandrel which will bend in planes perpendicular to each other.

3. A tube bending mandrel which comprises a rigid stem and a flexible body attached to the rigid stem, the exible body comprising four interconnected links, the intermediate links of the flexible body being pivotally interconnected at one end for relative movement therebetween in a rst plane only `and each connected slidably at its other end to an adjacent link for relative movement therebetween in a second plane, said rst and second planes being mutually perpendicular.

4. A tube bending mandrel for forming compound bends in a rectangular wave guide tube in planes mutually perpendicular to each other, which comprises arigid stem and -a flexible body pivotally attached to the rigid stem, the flexible body comprising four interconnected links of generally rectangular cross section, the intermediate links of the flexible body being pivotally interconnected at one end for relative movement therebetween in a tirst plane only and each connected slidably at its other end to an adjacent link for relative movement therebetween in a second plane, said rst and second planes being mutually perpendicular.

References Cited in the tile of this patent UNITED STATES PATENTS 847,094 Monnet et al Mar. 12, 1907 878,604 Brinkman Feb. 1l, 1908 1,683,573 Mueller et al. Sept. 4, 1928 1,841,592 Edwards Jan. 19, 1932 2,776,697 Serlaut Jan. 9, 1957 FOREIGN PATENTS 5,019 Great Britain of 1885 569,446 France Jan. 7, 192.4 

